The need to disinfect municipal and industrial waste water has gained increasing importance in view of increased environmental awareness and regulations mandating improved water quality. Such waste water has been disinfected with ultraviolet radiation in a number of methods and with a variety of apparatus. Such methodologies and apparatus typically include surrounding ultraviolet sources with protective jackets (hereinafter sometimes collectively referred to as "lamps") and submerging the lamps into the waste water as it flows through open or closed channels, open or closed containers or the like.
However, it has been a recurring and troubling problem that the transparent protective jackets surrounding the ultraviolet source become covered with particulate matter, residues, films and the like contained within the waste water over time. Of course, this covering builds up or increases in thickness over time and decreases the amount of ultraviolet light radiating outwardly from the lamps, thereby reducing the effective ultraviolet dose and decreasing disinfection efficiency. A number of attempts have been made to alleviate this problem. However, all attempts to date have resulted in apparatus which is either totally or partially ineffective, cumbersome to operate and maintain or economically prohibitive. For example, some apparatus utilizes structures that impedes the smooth flow of the waste water, requires additional power and personnel for operation, or causes the water to flow in patterns that reduce ultraviolet dosing efficiency.
Prior art known to the applicants includes U.S. Pat. Nos. 4,757,205, 4,899,056, 5,019,256 and 5,103,847. The most relevant of these patents utilize air to contact the transparent jackets to perform cleaning action. However, these systems involve the need to remove the transparent jackets and lamps from the waste water for treatment. Of course, this is a cumbersome process requiring periodic shut down of the system, extra operating personnel and equipment, and contributes to lowered efficiency of the entire system.